U.S. Pat. No. 8,687,769 B2 describes a rotatable anode for an X-ray tube, wherein the anode comprises a first unit adapted for being hit by a first electron beam and at least a second unit adapted for being hit by at least a second electron beam. Further, an X-ray system is described, which comprises an anode and a main cathode for generating an electron beam. The main cathode is adapted to generate a first electrical potential. The X-ray system further comprises an auxiliary cathode for influencing a second electrical potential.
WO 2013/076598 A1 describes an X-ray tube for faster, periodic modulation of a generated X-ray beam. The X-ray tube comprises an anode disk which comprises a circumferential target area with a target surface area, a focal track centre line, and a beam-dump surface area. The target surface area is provided such that, when being hit by an electron beam, X-rays for X-ray imaging can be generated; and the beam-dump surface area is provided such that, when being hit by an electron beam, no useful X-rays for X-ray imaging can be generated.
WO 2013/001384 A1 describes the generation of multiple energy X-ray radiation. In order to provide multiple energy X-ray radiation with increased switching frequencies, a rotating anode for an X-ray tube is provided with an anode body, a circular focal track, and an axis of rotation. The focal track is provided on the anode body and comprises at least one first focal track portion and at least one second focal track portion. Transition portions are provided between the at least one first and second focal track portions.
X-ray tubes may be equipped with segmented anodes. In a segmented anode, slits or slots are present radially inwards into the outer circumference of the anode to reduce thermal stress which arises from large temperature gradients during operation of the X-ray tube.
Upon anode rotation, an electron beam provided by a cathode repeatedly hits the slits. The anode outputs a photon flux when the electron beam hits the anode. If a focal spot width of the electron beam is small with respect to a width of a slit, the photon flux drops during passage, as X-rays are generated deep inside the slot and will neither enter the used electron beam nor reach an object in e.g. a CT scanner.
The photon flux drop or drop of intensity may pose an issue for the detection and reconstruction of an image, in particular when the X-ray detector reacts strongly non-linear. In other words, when a photon flux drops, the signal may rise sharply to a signal burst.
During passage of slits through the focal spot of the electron beam, these signal bursts appear to be random and add a noise, which can be significant and undesired.
As a result, it would be desired to keep the photon flux stable despite of the existence of the slits to increase the quality of image detection.